In a power conversion device that generates a three-phase AC voltage and supplies the three-phase AC voltage to a load by combining ON/OFF states of switching elements configuring a three-phase inverter of a PWM modulation system, the power conversion device detects phase currents flowing to a three-phase load such as a motor and controls the load on the basis of the phase currents.
As means for detecting the phase currents flowing to the three-phase load, there are a current sensor and a shunt resistor connected in series to the switching elements configuring the inverter.
As the configuration in which the shunt resistor is provided, there are a configuration in which a power-supply shunt resistor that detects an electric current between a DC power supply and an inverter device is provided and a configuration in which a lower-arm shunt resistor that detects a phase current of a relevant phase is provided between a lower-arm switching element and a minus side of the DC power supply.
In the configurations in which the power-supply shunt resistor and the lower-arm shunt resistor are provided, it is necessary to specify a phase current detected for each of phases. Control software is complicated. In the configuration in which the power-supply shunt resistor is provided, when only an electric current for one phase can be detected, it is necessary to perform energization control to detect electric currents for two phases. That is, a period in which the phase currents are detected in one switching cycle is limited to a narrow range. Therefore, an inverter device is disclosed that can detect, for example, by “providing a power-supply shunt resistor and lower-arm shunt resistors for at least two phases and detecting, with the power-supply shunt resistor, a phase current that cannot be detected by the lower-arm shunt resistors”, the phase current with simple control software (e.g., Patent Literature 1).